Propane dewaxing



June 15, 1937 Hjo. FORREST ET M. w 2,083,700 PROPANE DEWAXING I r Filed June 30, 1934 INVENTORS HerzrgQ Forraat La an H07 ATTORNEY Patented June 15.19 37 I I 2,083,706

usirspi STATES PATENT OFFICE.

Elisabeth, N. 1., assignors to Standard Oil Company, Chicago, 11]., a corporation of Indiana Application June 30, 1934, Serial: No. 733,258 I '1 Claims. (01. 196-18) This invention relates to-an improved method nature of thewax which isundergoing separaand means for applying auto-refrigeration to usetion and if the scrapers employed in the heat ful pu poses'and it pertains more particularly exchange apparatus tend to break up the wax to an improved propane dewaxing system. crystals and interfere with the later mechanical 5 It has been found that liquefied, normally gasseparation step, we may avoid the'indirect heat eous hydrocarbon diluents such as propane offer exchange entirely and obtain all of the cooling many extremely important advantages in the deby direct refrigeration. waxing of mineral oils. Such diluents permit or An important feature of this-invention i's-the cause the crystallization of wax in readily filmethod of introducing cold propane into the chill terable or. settleabie'form even though the wax chamber to replace the propanevaporized there- 10 is of such nature'that it could-not be commercially from. We prefer to introduce cold propane at filtered or settled from ordinary naphtha diluents. about -40 F. because wax-free propane may be Also, it has been foundthat rapid chilling rates readily cooled by heat exchange with the cold may be employed, that high yields of low pour filtrate. If this cold propane were introduced i5 point oils (relatively drywax cakes). are obtained, directly into a body of warm waxy oil solution '15 that extremely rapid filtration or settling can be there would be a shock chilling which would reused, and that removal of diluent from dewaxed suit in the formation of fine amorphous, nonoil actually supplies, refrigeration to the system filterable and non-settleable wax crystals.we and requires a minimum amount of heat a d therefore introduce the cold propane above the stripping stes'n. body of the propane-oil mixture in the chilling 20 I An object of 'our invention is to provide an imtank and we contact this cold propane with'vaproved method and means for cooling a propaneporized propane in the upper part' of the chamber oil-wax mixture to extremely low temperatures before the cold propane comes in contact with the without "shock chilling and without employing waxy solution. This contact in the upper part unduly large quantities of propane. A further of the chamber is preferably effected on bubble 25 object is to control the cooling and crystallization trays of the type used in thefractionating towers of wax, so that it will yield a dense and relatively of a distillation system, but any equivalent gas dry wax cake and a maximum yield of dewaxed, liquid contactmeans may be substituted therefor. low pour point oil. The condensation of warm propane vapors in the Normally gaseous diluents such as propane have newly added cold propane tends to warm up the 30 also been found to have unique properties in the cold propane, so that by the time it reaches the dessphalting of petroleum residues and/or in the liquid body'at the base of the chiller it is at sub- 1 "fractionation thereof into'components of higher stantially the same temperature as. that body. and lower average molecular weights. Thesesame A the Same time P p V p r r removed ggdiiuents have-been found to be extremeiy'useful from the upper part of the chiller in amounts in comblnatlofr with solvents for separating high egulated to obtain the desired rate of cooling and viscosity index or parafllnic fractions of oil from the introduction of cold propane is regulated to low viscosity index naphthenic fractions. Anjobserve as a reflux liquid, tomaintain the desired Ject of ourin'vention is to provide a chilling sysv propane concentration in the waxy oil propane 4o tem that will be useful in these processes. solution, to accomplish the necessary refrigera- 40 A further object is to utilize eflectively' the tion, and finally to reduce the viscosity of the large amount of refrigeration which is available chilled oil, so that it may be readily filtered or in the step of removing propane from propanesettled from the solidified wax. By' introducing oil solutions. Other-objects will be apparent as the cold propane at the top of the chiller and by the detailed description of our'invention proceeds. DaSS K 011B m bubble plates We 45 In applying our invention to propane dewaxing, tain chilling with a minimum amount of propane we introduce measuredamounts of propane and and we maintain'anextremely efficient and accucharging stockinto a mixing chamber to obtain rate method of controlling the temperature and a homogeneous mixture or solution of the way the rate of chilling. '50 oil in the propane; This mixture may then be This invention isparticularly useful for the recooled to approximately its cloud point by ordimoval of para mnic waxes which have a tendency nary cooling water and it may be further cooled .to form interlacing crystals and to occlude 011., by indirect heat exchange with cold filtrate. The So-calledpour point depressors" have been .amount of refrigeration which can'bemployed'in found to regulate wax crystallization and their 56 this manner is somewhat dependent upon the presence makes it possible to obtain denser wax under the same conditions without the pour point depressors. We have found that the oil itself contains crystallization regulators which are effective when only small amounts of propane are employed in the chilling step, but which are less eflective when large amounts of propane are present during the crystallization of the wax. In accordance with our invention it is possible to crystallize the wax by auto-refrigeration inthe presence of less than one volume of propane per volume of oil and we have found that this tends to give wax crystals that do not occlude appreciable amounts of oil; it tends to give large oil yield and dense wax cakes, particularly when the wax is of the crystalline type. We obtain all of the advantages of large propane volumes without their disadvantages and at the same time we obtain the benefit of pour point depressors in the oil itself. Additional cold propane may be added to the slurryjust before the filtration or settling step, but we avoid long standing of crystallized wax in propane solution; the wax is not very soluble in propane at dewaxing temperatures but long standing may result in deleterious re-arrangement of crystal formation. v a

In propane 'deasphalting the injection of extremely cold propane may cause the solidification of portions of'the asphalt in combination with the oil or, in other words, it causes the occlusion of oil in solidified asphalt. By employing our improved method'and means for adding propane to the system, the propane is at substantially the same tem perature as the asphaltic oil before it comes in contact with said 011 and it therefore produces an all solution which may be readily separated from' the insoluble asphalt phase. The introduction of propane in accordance with our improved method facilitates the subsequent. phase separationwlth 4 a minimum amount of propane.

r In the accompanying drawing we have shown a diagrammatic elevatlonal plan of our improved propane dewaxing system. The term propane" as used herein is expressly defined to cover equivalent normally gaseous diluents and particularly hydrocarbons of from two to, four or five carbon atoms and mixtures thereof. In other words, this expression is intended to include butane, ethane, propylene, butylene, etc. and mixtures thereof either alone or in combination with halogenated substitution products of methane and ethane, normally gaseous ethers, sulfur diomde. methyl amine, etcm This invention relates to the technique of employing normally gaseous diluents and it is not dependent upon the use of any specific diluent.

The invention may be employed for the dewaxing of any wax-bearing oil, but it is particularly useful in the dewaxing of petroleum distillates or petroleum residues from which asphalt has been separated. The invention is also useful.

tion relates to an improved'mixing and chilling technique. but since the chilling is of particular importance in the propane dewaxlng system its application in that field will be described ass.

preferred embodiment of the invention.

Propane from high pressure storage cylinders in may be selectively withdrawn through outlets I I and lines i2 and i3 by pump l4 to heater l5 and mixer IS. The oil stock is introduced from line I! by pump i8 which may be driven by the same motor, I9 which drives pump H. means may be employed for proportioning the propane feed with the feed of charging stock. If the charging stock is an S. A. E. 50 Mid-Continent distillate, it may have a pour point of about F., so that it will be introduced into the system at about'this temperature. In that case sufilcient steam is used in exchanger i5 to warm the propane to substantially an equivalent temperature. Any suitable mechanical mixing means may be employed in mixer l6 and in fact a homogeneous solution of both the oil and wax intne' propane may be obtained by warming the mixture to a suiflciently high temperature (usually about low its cloud point, but not low enough to pro duce solidification of appreciable amounts of wax or the accumulation of wax in the exchanger. In

80 F. to F.)rby means of steam coil 20. Also,

Any equivalent some cases it may be desirable to pass the mixture directly from exchanger 24 through pipe 26 to the batch cooler hereinafter described, by-passing entirely indirect heat-exchanger 25. Also we may.

by-pass exchanger 24 and introduce the solution directly from mixer I6 to the batch cooler, or we may pass it through line 21, line 28 and exchanger 25 to the batch cooler.

Exchanger 25 may be of the indirect type wherein scrapers or other mechanical means are employed for removing wax from the heat exchange surfaces. For instance, this exchanger may consist of the well known Carbondale chiller in which the propane-oil mixture flows through the center of a tube and the chilling medium flows in a Jacket around the outside of the tube, waxy oil being propelled through the tube and scraped from the sides thereof by means of a screw con-v veyor. This indirect heat exchange means may be .designed as a continuous cooler discharging into any one of a plurality of batch coolers, as hereinafter described, or it may itself be a batch cooler. The cooling medium which is introduced through'pipe 28 and which is circulated' through the jackets or heat exchange devices is preferably cold. dewaxed filtrate. The propane-oil-wax slurry maybe chilled in exchanger 24 and/or exchanger 25 from about 80 F. to 30 F; or about 60 F; to 30 F., depending" largely upon the type of oil undergoing the dewaxing and the nature of the heat exchangers, scrapers, etc.

Partially cooled slurry maybe filtered at this point or it may be introduced by line 29 into batch cooler 30; Batch cooler 30 is preferably a pressure vessel whichhas been especially fabricated or treated to withstand low temperatures.

If continuous exchangers are employed, we will use a plurality of these batch coolersin rotation. When sufilcient solutes have been charged tothe cooler 30, the inlet valve is -closed and cooling is started by the introduction of cold propane at about -40 F. from storage tank 3| through line 32 and valve 33. This propane l'snot injected div rectly into the body of slurry in the base of cooler so, but is introducedon a bubble plate '34. -so

that propane which is directly to the liquid in the lower' part 0! the chill.

prefer to employ one or more additional bubble plates 88 and to introduce the liquid from the lower run-down pipe. 39 to the body oi liquid in the base of the chiller. By the time the liquid propane reaches line 38 it is warmed up to approximately the temperature of theoll-wax slurry. so.that its introduction in this manner does not cause shock chilling. For some purposes it is desirable to pump propane irom plate 88 through line 39A by means of pump 8913 into the bottom 0! the chiller; this reduces the height required and it also provides adequate in the chill chamber.

The removal of vapors from the top oi the tower, together with-the addition or cold pro pane, causes a gradual lowering of the temperature. By employing this 'method oi cooling we chamber; but we may maintain a constant diluent ratio'or we may diluent ratio.

80 constantly increase or-dec'rease the depending upon the amount or liquid prop ne introduced through valve 83 as compared with the amount oi propane vapors withdrawn through pipes '86 and 86. when we are dewaxlng parafiln 35 distiiiates and/or removing .wax which .has a tendency to form in lacing crystals and to coclude oil.- we find it is desirable to begin the chilling with a relatively small and to introduce the bull; oi gIO'beIore-the filtration step. We have icund that I most liquid level gauges are inoperative in this. apparatus because of the tendency tor propane to vaporize in the gauge, the tendency oi wax and oil to plug up openings. etc. We have so. discovered. however, that storagetankorchillermaybeaccurately indicated-stall times by means of an intern l ;fioat designed to operate an indicator through a nun so indicator-ls oithis true: the

the diluent just etic clutch' 'Ihe mils-hue" liquid level nest is operatively connectedto arotating' magnetic core which may magnetic indicator means we may use such a liquid levelcontrol torautomaticallv the amount oi propane which. isjntroduced through valve N. --Excel1ent filterrates can-be obtained when the chilling means of pipe ll ".which'acts a .16 type.butwhichare I When the chilling havbeeu efleotcd: add additions-1' through lines I! and 41 to the inlet i '1 l- 'inaccncentratedsolutiomwomay i 0014 side oi pump 13. or through lines 82 and "a to iti i-tlieniletsideoipumpll. Weprcier..to fiiter wi h .lected in tank lower run-down circulation and agitation therein instead of toheat exchanger a'r'n'ount oidiluent .the liquid level in a be a block' of magnetized iron and the rotation; of this magnet .core causes the actuation. oi outside of the vessel 'to saidgas lineaior the Filter slurry supply tuned to. about" from thebase oi Blurr is pumpe M by b p. -46. tofiiters ll which may be of the multiple batch 'oil in-propalie tor crystallizing wax in about 2 to l volumes oi propane per volume of oil. 1

Filtrate is withdrawn through lines (and colthrough conduits $0 to wax pct H which act a a su'rgetank or recovery system, the waxy mixture being forced by pump. through line into high pressure still 54 and then being passed through pipe as and pressure release valve 66 to low pressure still 81. lsvax is withdrawn from the system through pipe 8.

We prefer to maintain a low pressure gas line .59 connectedto the intake side of holding compressor 60 which discharges the compressed propane through condenser SI and pipe 82 to propane storage tanks Ill. Cold propane storage tank II is connected to the low'pressurelin'e through pipe 63, the chiller is connected thereto through pipe .84,

filtrate storage means. through pipe 65, low pressure wax still through pipe 66, etc.

we may utilize a high pressure gas line 81 which leads through condenser 68 ,back to storage tanks i0 and which usually requires no compressors although compressor 69 may be s d it necessary. High pressure wax still 54 is con. nectedby pipe 10 to the high pressure gas li 61. Wax surge tank .5! may be connected either to line ,8! through pipe 1i or line 69 through pipe 12; thus we may warm, up the wax in this tank by condensing high pressure propane vapors i using a heater in the tank. Filtrate from surge tank or receiver 49 is passed through line II b'y'p p 14 to line 28 for cooling the incoming propane-oil-wax mixture. Part or all of the filtrate mayalso be passed by pipe 16 ii for cooling the-propane in pipe" which-is flowing .to cold propane reservoir 8|.

'-I ."he propane-filtrate mixture which has been exchange as hereinabove dcby heat scribed is introduced by nine '28 into high pressure filtrate still [8 which is vented by line 19 to high-pressure gas line 61. The liquid. from this still is passed through line 8ll-and pressure reducing .valve ll to low pressure nitrate still 82 which is vented by line ll'tolow pressure propane line' It. Demed' oil is removed from the systemthrough'linefl .Wbile we have shown low I sa line. that we may also use gas and that we may connect tures and pressures. Pipe 88 may connected to high pressure gas line 81 sotha ot.propane to introduction of a charge .0! waxyoil solution,

tank '41 is preierably' 'con-. netted to low pressure. II. Also, the filters m be connected either to the high pressure or the low. pres-mire gas-line for claims the prior; art will permit.

Wsclainn' .1. 'Ihsniethod-oi chilling a solution oi wea y term which comprises introducing said solution introintc'a closed chillingsone underprcssm'o 49. The wax cake is withdrawn.

reservoir tor. feeding the wax gas line I59 through -PiP ahigh pressure and a' it should be understood. lines of intermediateregulation of .t'emperavaporamay'be heed to warm up-the chiller prior.-

the regulation oi'ternperaturea and ressure dean: p e r d a llowins- 4 V I I chilling zone, directly contacting said cold prop n 'wi hpropane vapors from said solution whereby the heat of condensation warms up in spropane before it is admixed wlththe 5 propane solution in the lower part pi the chill n some and admiring introduced-propane wi h the solution in the lower part of the chilling zone.

2. The process of claim 1 which includes the step of removing 'propane'vapors from the upper part of'saidzone. r

8. The method of chilllng a propane solution .01 waxy oil for the production of fllterable'wax. crystalsiwhich omprises introducing the solu tion into a closed chilling zone. withdrawing pro pane valporsirom the top of said chilling zone. introducing cold liquid propane near the top of said chilling zone, directlycontacting said cold propane with propanevaporized from said SON-1':

tion whereby the introduced propane-is brought into temperature equilibrium with the solution before itis'admixed therewith. admixing the introduced propane with the solution in the chilling zone andregulating the'amount oi propane introduced and the amount of propane withdrawn 25,,tomaintain the optimum diluent ratio.

- "4. 'Ihe method 01. chilling. a propane solution oi waxy oil containing natural wax crystallization regulators for the preparation oi fllterable wax crystals which comprises introducing a,solution of waxy oil in less than-an equal volume otpropane into=a chilling zone-withdrawing propane vapors-from the top of said chilling zone, introducing cold propane near the top at said chilling zone, intimately contacting the propane vapors in said zone with'the introduced cold propane whereby the latter is brought into temperature '-e quilibrium with the propane solution prior-to admixture thereto, admixing the introduced propane with said solution, and regulating the rate 40 of introducing and-removing propane to maintain the propane ratio 01 the solution less than l'to' l by volume until. the wax has been solidified in fllferable form. 1 1

P as No-.; 2.083.700.

pane with propane vapors from said solution in lower part-0t said zone.'

. chilling zone to supply agitation therein 5 nnmir'-o..ronensr;' hr in.

5. The method of chilling a propane solution of w'aw oil dissolved in about 'fl-nequal volumeof propane at a relatively high temperature, 5 which comprlsespartially cooling said mixture by indirectheat exchange, introducing the p'm-I 5 tially cooled solution into a closed chilling zon vaporizing propane from the solution in said chilling none. introducing cold liquid propane at the top of said chilling zone out of contact with the solution therein, condensing propaneyapors in the cold liquid propane to bring it intotem. perature equilibrium with thepropane solution. introducing the warmed propane into the solution in the lower part of the zone, midiing propane vapors from the.top of said chilling -zone at a rate to maintain the ratio of propane -to waxy oil at about 1 to 1 during the rem-m into a closed chilling zone under pressure. vaporizing propane from said solution and removing propane-vapors from said none, introducing cold propane at the upper part of said zone and irom the upper part into the solution in the'lower part of saidzone at substantially the same rate that the propane is removed therefromso that the liquid level in said zone will remain substantially constant. and directly contacting said cold p the upper part of-said'zone whereby the heat of condensation warms up incoming propane before it is admixed with the propane solution in the 3 7. The method of claim 6 wherein propane which warmed in the upper part of the chilling zone is injected in the lower part of the a HENRY 0. FORREST. LEE VAN HORN.

a-mam or coa'sscr'ion.

June is. 1957..

It whereby certified that error appears. "in the prlnteds'pecificat'im of the above numbered patent requiring correction as follows: Page 4,

first column, l'ine-g5, .claim 5, strike out the words "the optimum diluent. -ratio". and insert instead azsubstantiallyconstant liquid level in the;

correction therein the Patent Office;

Signed. and

- (Scotti chilling z one and that the said Letters Patent should, be read with this thatthe-s ame lfiayiconform-t'o the record of the' case in sealed-"this 27th day o r".ru1 y-.- i. n.- 1937.

nryvaniredaic Acting campaignin Patient-g" 4 V I I chilling zone, directly contacting said cold prop n 'wi hpropane vapors from said solution whereby the heat of condensation warms up in spropane before it is admixed wlththe 5 propane solution in the lower part pi the chill n some and admiring introduced-propane wi h the solution in the lower part of the chilling zone.

2. The process of claim 1 which includes the step of removing 'propane'vapors from the upper part of'saidzone. r

8. The method of chilllng a propane solution .01 waxy oil for the production of fllterable'wax. crystalsiwhich omprises introducing the solu tion into a closed chilling zone. withdrawing pro pane valporsirom the top of said chilling zone. introducing cold liquid propane near the top of said chilling zone, directlycontacting said cold propane with propanevaporized from said SON-1':

tion whereby the introduced propane-is brought into temperature equilibrium with the solution before itis'admixed therewith. admixing the introduced propane with the solution in the chilling zone andregulating the'amount oi propane introduced and the amount of propane withdrawn 25,,tomaintain the optimum diluent ratio.

- "4. 'Ihe method 01. chilling. a propane solution oi waxy oil containing natural wax crystallization regulators for the preparation oi fllterable wax crystals which comprises introducing a,solution of waxy oil in less than-an equal volume otpropane into=a chilling zone-withdrawing propane vapors-from the top of said chilling zone, introducing cold propane near the top at said chilling zone, intimately contacting the propane vapors in said zone with'the introduced cold propane whereby the latter is brought into temperature '-e quilibrium with the propane solution prior-to admixture thereto, admixing the introduced propane with said solution, and regulating the rate 40 of introducing and-removing propane to maintain the propane ratio 01 the solution less than l'to' l by volume until. the wax has been solidified in fllferable form. 1 1

P as No-.; 2.083.700.

pane with propane vapors from said solution in lower part-0t said zone.'

. chilling zone to supply agitation therein 5 nnmir'-o..ronensr;' hr in.

5. The method of chilling a propane solution of w'aw oil dissolved in about 'fl-nequal volumeof propane at a relatively high temperature, 5 which comprlsespartially cooling said mixture by indirectheat exchange, introducing the p'm-I 5 tially cooled solution into a closed chilling zon vaporizing propane from the solution in said chilling none. introducing cold liquid propane at the top of said chilling zone out of contact with the solution therein, condensing propaneyapors in the cold liquid propane to bring it intotem. perature equilibrium with thepropane solution. introducing the warmed propane into the solution in the lower part of the zone, midiing propane vapors from the.top of said chilling -zone at a rate to maintain the ratio of propane -to waxy oil at about 1 to 1 during the rem-m into a closed chilling zone under pressure. vaporizing propane from said solution and removing propane-vapors from said none, introducing cold propane at the upper part of said zone and irom the upper part into the solution in the'lower part of saidzone at substantially the same rate that the propane is removed therefromso that the liquid level in said zone will remain substantially constant. and directly contacting said cold p the upper part of-said'zone whereby the heat of condensation warms up incoming propane before it is admixed with the propane solution in the 3 7. The method of claim 6 wherein propane which warmed in the upper part of the chilling zone is injected in the lower part of the a HENRY 0. FORREST. LEE VAN HORN.

a-mam or coa'sscr'ion.

June is. 1957..

It whereby certified that error appears. "in the prlnteds'pecificat'im of the above numbered patent requiring correction as follows: Page 4,

first column, l'ine-g5, .claim 5, strike out the words "the optimum diluent. -ratio". and insert instead azsubstantiallyconstant liquid level in the;

correction therein the Patent Office;

Signed. and

- (Scotti chilling z one and that the said Letters Patent should, be read with this thatthe-s ame lfiayiconform-t'o the record of the' case in sealed-"this 27th day o r".ru1 y-.- i. n.- 1937.

nryvaniredaic Acting campaignin Patient-g" 

